The present invention relates to grill filter assemblies for forced air systems for residential and commercial heating and air conditioning systems. Most residential and commercial forced air systems include filters for purifying the air circulated therein, at least to the level of removing dust and other particulate matter. Specialized filters including chemicals or a static electric charge are available for both residential and commercial systems to enhance the removal of high levels of airborne contaminates including bacteria, moisture, odors and pollens as well as common dust and similar particulates.
Commercial and residential heating and air conditioning systems conventionally include the filter means in a central location such as the location of the blower for circulating the heated or cooled air. Most residential systems have only one blower, which is located within the housing containing the heater chamber and/or the air conditioning evaporator. As should be well appreciated, such units are located in attics, basements, utility rooms and the like, usually being out of ready access and requiring substantial effort to open the unit to gain access to the filter for replacement. Washable filters of woven or non-woven synthetic fabric or metallic thread prolong the replacement exercise by requiring the system to be down for the time the service technician removes the filter, takes it to a suitable location for cleaning and then returns for reinstallation of the filter.
As will also be appreciated, such filters for centralized systems are frequently large in order to be able to handle the air flow of the full system, and handling of such filters is a bulky and a cumbersome task. If the filter is capable of removing high levels of pollutants, as by being a part of a precipitation system, removal for cleaning or replacement is a more complicated procedure requiring additional time and thus being more expensive. For among these and other reasons, filters for centralized systems are less frequently cleaned or replaced as recommended, leading to build-up of particulate matter on the filter interfering with circulation of the air. Particulate build-up on filters also induces the circulated air to seek alternative routes (e.g., leaks) providing less back pressure to flow which may cause loss of efficiency of the over-all system and/or the circulation of unfiltered air.
While there are a number of grill filter systems which have been developed for application to either or both of forced air vents or returns, all are of complex construction or requiring significant installation procedures. U.S. Pat. No. 4,334,899 to McConnell is a multiple-framed device requiring significant preparation of the duct opening before installation of the unit. Likewise, location of the filter within the grill mechanism complicates replacement of the contained filter. Similarly, U.S. Pat. No. 5,176,570 to Leidl illustrates a grill filter assembly for a cold air return for a forced air system. This design also includes a complex frame system for surrounding and connecting to the forced air duct. According to the patent specification, the grill filter is adapted to be attached to the baseboard or wall surrounding the return duct and no interaction with the duct other than being placed in close proximity assures that the return air will be forced to flow through, rather than around the filter system.
U.S. Pat. Nos. 5,240,487 to Kung and 5,472,380 to Sarazen, et al, illustrate floor type grill registers including replaceable filters, and in '487 the capability to dispense scents into the air stream. As may be appreciated, the floor mountings of the illustrated grill filters varies substantially from the wall or ceiling mounted varieties.